Inkjet printing equipment

Abstract

To provide an inkjet printing device that can reduce waste ink. [Solution] The inkjet head 11 has a plurality of nozzles 16, each positioned at a different height. The pressure generating unit 23 discharges ink from each nozzle 16 by pressurized purging. During maintenance of the inkjet head 11, the control unit first discharges ink from each nozzle 16 by pressurized purging with a purging pressure suitable for the reference nozzle (all nozzles 16 except the highest nozzle 16) using the pressure generating unit 23, and then controls the nozzles 16 higher than the reference nozzle to perform flushing, with the amount of ink discharged increasing for each nozzle 16 at a higher position.

Description

Technical Field

[0001] The present invention relates to an inkjet printing apparatus.

Background Art

[0002] There is known an inkjet printing apparatus in which an inkjet head is arranged so as to be able to eject ink in a horizontal direction and print on a vertical plane (see Patent Document 1).

[0003] Further, as an operation for maintaining an inkjet head in an inkjet printing apparatus, an operation of discharging ink from nozzles of the inkjet head by pressure purge to remove thickened ink or the like from the nozzles, and then removing ink, thickened ink or the like adhering to the inkjet head with a wiper is known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above-described inkjet printing apparatus for printing on a vertical plane, a plurality of nozzles formed in the inkjet head are arranged in the vertical direction, and the height positions of the respective nozzles are different. For this reason, the head difference between each nozzle and an ink tank connected to the inkjet head is different. As a result, the nozzle pressure becomes smaller for nozzles at higher positions.

[0006] Therefore, in pressure purge, nozzles at higher positions require a higher purge pressure. Thus, when pressure purge is performed at a purge pressure suitable for the nozzles at the highest position, the amount of ink discharged from the other nozzles becomes excessive. As a result, the waste ink generated during maintenance increases.

[0007] The present invention has been made in view of the above, and aims to provide an inkjet printing apparatus that can reduce waste ink. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides an inkjet printing apparatus comprising: an inkjet head having a plurality of nozzles arranged at different height positions; a purging unit that discharges ink from the plurality of nozzles by pressurized purging; and a control unit that, during maintenance of the inkjet head, discharges ink from the plurality of nozzles by pressurized purging at a purging pressure suitable for a reference nozzle, which is one of the nozzles other than the highest-positioned nozzle, and then controls each of the nozzles positioned higher than the reference nozzle to perform flushing in which the amount of ink discharged increases with the position of the nozzle. [Effects of the Invention]

[0009] According to the inkjet printing apparatus of the present invention, waste ink can be reduced. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram showing the configuration of an inkjet printing apparatus according to an embodiment. [Figure 2] This is a schematic diagram of the transport and printing sections. [Figure 3] This figure shows the capping position and retracted position of the cap. [Figure 4] This is a schematic diagram of the ink unit's configuration. [Figure 5] This is a schematic diagram of the maintenance department. [Figure 6] This is a flowchart illustrating the operation during inkjet head maintenance. [Figure 7] This is a flowchart of the ink suction process. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals.

[0012] The embodiments shown below illustrate devices and the like that embody the technical concept of this invention, and the technical concept of this invention does not specify the material, shape, structure, arrangement, etc., of each component as described below. The technical concept of this invention can be modified in various ways within the scope of the claims.

[0013] Figure 1 is a block diagram showing the configuration of an inkjet printing apparatus according to an embodiment of the present invention. Figure 2 is a schematic diagram of the transport section and printing section of the inkjet printing apparatus shown in Figure 1. Figure 3 is a diagram showing the capping position and retracted position of the cap of the inkjet printing apparatus shown in Figure 1. Figure 4 is a schematic diagram of the ink unit of the inkjet printing apparatus shown in Figure 1. Figure 5 is a schematic diagram of the maintenance section of the inkjet printing apparatus shown in Figure 1.

[0014] In the following explanation, the direction perpendicular to the plane of the paper in Figure 2 is defined as the front-to-back direction, and the front of the paper is defined as the front. Also, the top, bottom, left, and right directions of the paper in Figure 2 are defined as the up, down, left, and right directions. The up and down direction is the vertical direction, and the left and right directions and the front-to-back direction are perpendicular to each other, and both are perpendicular to the up and down direction and parallel to the horizontal direction.

[0015] As shown in Figure 1, the inkjet printing apparatus 1 according to this embodiment comprises a transport unit 2, a printing unit 3, a plurality of ink units 4, a maintenance unit 5, and a control unit 6.

[0016] The conveying unit 2 conveys a printing medium (not shown). The printing medium has a printing surface which is a vertical plane perpendicular to the horizontal direction in a state where the printing medium is placed on the conveying unit 2 and conveyed, and on which printing is performed by the printing unit 3. The printing medium is, for example, a cardboard box whose side surface is the printing surface.

[0017] The printing unit 3 performs printing on the printing medium conveyed by the conveying unit 2. As shown in FIGS. 1 and 2, the printing unit 3 includes a plurality of inkjet heads 11, a plurality of caps 12, a plurality of cap driving units 13, and a head holder 14.

[0018] The inkjet head 11 ejects ink in the horizontal direction toward the printing medium conveyed by the conveying unit 2. In the present embodiment, eight inkjet heads 11 are arranged in a staggered pattern. That is, the eight inkjet heads 11 form four head rows each consisting of two inkjet heads 11 arranged vertically. And the second and fourth head rows from the left are displaced downward by half the distance between the inkjet heads 11 in the vertical direction with respect to the first and third head rows.

[0019] The inkjet head 11 has a plurality of nozzles 16 that eject ink in the horizontal direction. The plurality of nozzles 16 are arranged along the vertical direction (perpendicular direction) and are arranged at different height positions. The plurality of nozzles 16 open to the nozzle surface 11a of the inkjet head 11. The nozzle surface 11a is the front vertical plane of the inkjet head 11.

[0020] The cap 12 is a member that abuts against the nozzle surface 11a of the inkjet head 11 for capping. The cap 12 is provided corresponding to each inkjet head 11 one by one.

[0021] The cap 12 is movable between the capping position shown by the solid line in Figure 3 and the retracted position shown by the dashed line. The capping position of the cap 12 is the position where it contacts and caps the nozzle surface 11a of the inkjet head 11. The retracted position of the cap 12 is a position adjacent to the right side of the inkjet head 11.

[0022] The cap 12 is positioned in the capping position when pressurized purging and flushing, described later, are performed, and receives the ink discharged from the nozzle 16 by pressurized purging and the ink ejected from the nozzle 16 by flushing. The cap 12 is also positioned in the capping position when the ink suction process, described later, is performed, and functions as a space for suction of ink by transmitting the negative pressure (suction pressure) generated in the waste ink tank 26, described later, by the pressure generation unit 23. The cap 12 is positioned in the retracted position during printing and when the nozzle surface 11a is wiped by the wiper 62, described later.

[0023] The cap drive unit 13 moves the cap 12 between the capping position and the retracted position. The cap drive unit 13 includes a motor (not shown). One cap drive unit 13 is provided for each cap 12.

[0024] The head holder 14 holds multiple inkjet heads 11, multiple caps 12, and multiple cap drive units 13.

[0025] The ink unit 4 supplies ink to the inkjet head 11. One ink unit 4 is provided for each inkjet head 11. As shown in Figures 1 and 4, the ink unit 4 includes an ink circulation unit 21, an ink replenishment unit 22, a pressure generation unit (corresponding to a purge unit) 23, a pressurized air path 24, a negative pressure air path 25, a waste ink tank 26, a waste ink path 27, and a suction air path 28.

[0026] The ink circulation unit 21 supplies ink to the inkjet head 11 while circulating the ink. The ink circulation unit 21 includes a pressurized tank 31, a pressurized tank liquid level sensor 32, a negative pressure tank 33, a negative pressure tank liquid level sensor 34, a pressurized ink path 35, a negative pressure ink path 36, a pump liquid delivery path 37, and an ink pump 38.

[0027] The pressurized tank 31 stores the ink to be supplied to the inkjet head 11. The pressurized tank 31 is subjected to positive pressure by the pressure generating unit 23 to deliver the ink to the inkjet head 11.

[0028] The pressurized tank liquid level sensor 32 is used to detect whether the liquid level of the ink in the pressurized tank 31 has reached a reference height. The pressurized tank liquid level sensor 32 outputs an "ON" signal when the liquid level in the pressurized tank 31 is above the reference height, and outputs an "OFF" signal when it is below the reference height.

[0029] The negative pressure tank 33 receives and stores ink that is not consumed by the inkjet head 11. The negative pressure tank 33 also stores ink supplied from the ink supply unit 22. The negative pressure tank 33 is supplied with negative pressure by the pressure generation unit 23 to recover ink from the inkjet head 11.

[0030] The negative pressure tank liquid level sensor 34 is used to detect whether the liquid level of the ink in the negative pressure tank 33 has reached a reference height. The reference height in the negative pressure tank 33 is the same as the reference height in the pressurized tank 31. The negative pressure tank liquid level sensor 34 outputs an "on" signal when the liquid level in the negative pressure tank 33 is at or above the reference height, and outputs an "off" signal when it is below the reference height.

[0031] The pressurized ink path 35 connects the pressurized tank 31 and the inkjet head 11. Ink supplied from the pressurized tank 31 to the inkjet head 11 flows through the pressurized ink path 35.

[0032] The negative pressure ink path 36 connects the inkjet head 11 and the negative pressure tank 33. Ink that is not consumed by the inkjet head 11 and is recovered into the negative pressure tank 33 flows through the negative pressure ink path 36.

[0033] The pump delivery path 37 is the path through which ink flows when the ink pump 38 delivers ink from the negative pressure tank 33 to the pressurized tank 31. In the direction of ink circulation, the upstream end of the pump delivery path 37 is connected to the negative pressure tank 33, and the downstream end is connected to the pressurized tank 31.

[0034] The ink pump 38 delivers ink from the negative pressure tank 33 to the pressurized tank 31. The ink pump 38 is located in the middle of the pump delivery path 37.

[0035] The ink supply unit 22 supplies ink to the negative pressure tank 33 of the ink circulation unit 21. The ink supply unit 22 comprises an ink cartridge 41, an ink supply path 42, and an ink supply valve 43.

[0036] The ink cartridge 41 contains the ink used for printing by the inkjet head 11. The ink in the ink cartridge 41 is supplied to the negative pressure tank 33 of the ink circulation unit 21 via the ink supply path 42.

[0037] The ink supply path 42 connects the ink cartridge 41 and the negative pressure tank 33. Ink flows from the ink cartridge 41 to the negative pressure tank 33 through the ink supply path 42.

[0038] The ink supply valve 43 opens and closes the ink flow path in the ink supply path 42. The ink supply valve 43 is opened when supplying ink to the negative pressure tank 33.

[0039] The pressure generation unit 23 generates pressure for ink circulation in the pressurized tank 31 and the negative pressure tank 33 of the ink circulation unit 21. Specifically, during ink circulation (printing operation), the pressure generation unit 23 draws air from the negative pressure tank 33 via the negative pressure air path 25 and sends air to the pressurized tank 31 via the pressurized air path 24, thereby applying positive pressure to the pressurized tank 31 and negative pressure to the negative pressure tank 33.

[0040] Furthermore, the pressure generation unit 23 draws air from the negative pressure tank 33 via the negative pressure air path 25 and sends air to the pressurized tank 31 via the pressurized air path 24, thereby applying positive pressure (purge pressure) for the pressurized purging process described later to the pressurized tank 31 of the ink circulation unit 21. In addition, the pressure generation unit 23 draws air from the waste ink tank 26 via the suction air path 28, thereby generating negative pressure (suction pressure) in the waste ink tank 26 for the ink suction process described later.

[0041] The pressure generation unit 23 has sensors that detect the pressure in the pressurized tank 31, the negative pressure tank 33, and the waste ink tank 26, respectively.

[0042] The pressurized air path 24 connects the pressure generating unit 23 to the air layer above the ink level in the pressurized tank 31.

[0043] The negative pressure air path 25 connects the pressure generation unit 23 to the air layer above the ink level in the negative pressure tank 33.

[0044] The waste ink tank 26 receives and stores the ink collected by the cap 12 during the pressurized purging process described later, via the waste ink path 27. The waste ink tank 26 also receives and stores the ink collected from the nozzle 16 during the ink suction process described later, via the waste ink path 27.

[0045] The waste ink path 27 is the path through which ink flows from the cap 12 to the waste ink tank 26.

[0046] The suction air path 28 connects the pressure generating unit 23 to the air layer above the ink level in the waste ink tank 26.

[0047] Furthermore, the cap 12, pressure generating unit 23, waste ink tank 26, waste ink path 27, and suction air path 28 constitute a suction unit that sucks ink from the nozzle 16.

[0048] The maintenance unit 5 wipes the nozzle surface 11a of the inkjet head 11. When wiping the nozzle surface 11a, the maintenance unit 5 is positioned in a deployed position adjacent to the front of the printing unit 3. When not wiping the nozzle surface 11a, the maintenance unit 5 is positioned in a retracted position, moved away from the deployed position.

[0049] As shown in Figure 5, the maintenance unit 5 comprises a wiper unit 51, a wiper drive unit 52, two guide rails 53, and two connecting members 54. Figure 5 shows the maintenance unit 5 in the deployed position.

[0050] The wiper unit 51 wipes the nozzle surface 11a of the inkjet head 11 to remove ink and other substances from the nozzle surface 11a. The wiper unit 51 comprises a wiper base 61 and four wipers 62.

[0051] The wiper base 61 is to which the wiper 62 is attached. The wiper base 61 has a screw hole 61a formed therein. A ball screw 67, which will be described later, passes through and is screwed into the screw hole 61a. The wiper base 61 moves vertically as the ball screw 67 rotates.

[0052] The wiper 62 is a component that wipes the nozzle surface 11a of the inkjet head 11. The wiper 62 is fixed to the lower surface of the wiper base 61. When the maintenance unit 5 is in the deployed position, the wipers 62 are positioned so that one wiper 62 is on the extension of each of the four rows of heads.

[0053] The wiper drive unit 52 moves the wiper unit 51 in the vertical direction. The wiper drive unit 52 includes a wiper motor 66 and a ball screw 67.

[0054] The wiper motor 66 rotates the ball screw 67.

[0055] The ball screw 67 rotates when driven by the wiper motor 66, causing the wiper unit 51 to move vertically.

[0056] The guide rails 53 extend vertically and guide the wiper unit 51 as it moves vertically. The two guide rails 53 are spaced apart from each other in the left-right direction. The left guide rail 53 guides the left end of the wiper base 61, and the right guide rail 53 guides the right end of the wiper base 61.

[0057] The connecting member 54 extends along the left-right direction and connects the two guide rails 53 to each other. The two connecting members 54 are spaced apart from each other in the vertical direction. The upper connecting member 54 connects the upper ends of the two guide rails 53, and the lower connecting member 54 connects the lower ends of the two guide rails 53.

[0058] The control unit 6 controls the operation of each part of the inkjet printing device 1. The control unit 6 is composed of a CPU, RAM, ROM, hard disk, etc.

[0059] During maintenance of the inkjet head 11, the control unit 6 performs a pressurized purge to discharge ink from each nozzle 16. At this time, the control unit 6 uses the pressure generation unit 23 to discharge ink from each nozzle 16 with a pressurized purge pressure appropriate for the lowest nozzle 16 (corresponding to the reference nozzle) among the nozzles 16 of the inkjet head 11. After the pressurized purge, the control unit 6 controls the flushing of each nozzle 16 other than the lowest nozzle 16 so that the amount of ink discharged increases with the position of the nozzle 16.

[0060] As mentioned above, each nozzle 16 of the inkjet head 11 is at a different height. Therefore, each nozzle 16 has a different head difference between it and the pressurized tank 31 and the negative pressure tank 33. As a result, the nozzle pressure decreases as the nozzle 16 is positioned higher. Consequently, if pressurized purging is performed with a purging pressure suitable for the highest nozzle 16, the amount of ink discharged from the other nozzles 16 will be excessive.

[0061] Therefore, in the inkjet printing device 1, as described above, pressurized purging is performed at a purge pressure suitable for the lowest position nozzle 16. Here, the purge pressure suitable for the lowest position nozzle 16 is preset. Then, for each nozzle 16 other than the lowest position nozzle 16, the purge pressure is insufficient, and as described above, flushing is performed by ejecting ink from these nozzles 16. At this time, the amount of ink ejected during flushing is increased for nozzles 16 at higher positions. This reduces the amount of waste ink generated during maintenance while suppressing a decrease in the effectiveness of removing thickened ink, etc., from each nozzle 16.

[0062] Here, the amount of ink ejected during flushing from each nozzle 16 is preset according to its respective height position. The amount of ink ejected during flushing may be adjusted by the number of times flushing is performed, or by adjusting the amount of ink ejected during a single flush.

[0063] Next, we will explain the operation of the inkjet printer 1 during printing.

[0064] When a print job is input, the control unit 6 starts ink circulation in the ink circulation section 21 of each ink unit 4. Specifically, in each ink unit 4, the control unit 6 uses the pressure generation unit 23 to generate the respective set pressures for ink circulation in the pressurized tank 31 and the negative pressure tank 33. As a result, ink circulation in the ink circulation section 21 begins, and ink flows from the pressurized tank 31 through the inkjet head 11 to the negative pressure tank 33.

[0065] When ink circulation begins in the ink circulation section 21 of each ink unit 4, the control unit 6 starts executing the print job. Specifically, the control unit 6 controls the transport section 2 to transport the printing medium and eject ink from each inkjet head 11 of the printing section 3 to print an image onto the printing medium.

[0066] During the execution of a print job, ink is supplied from the pressurized tank 31 to the inkjet head 11, and any ink not consumed by the inkjet head 11 is recovered in the negative pressure tank 33. When the pressurized tank liquid level sensor 32 is off and the negative pressure tank liquid level sensor 34 is on, the control unit 6 drives the ink pump 38. This causes ink to be sent from the negative pressure tank 33 to the pressurized tank 31. When the pressurized tank liquid level sensor 32 turns on, the control unit 6 stops the ink pump 38. In this way, ink is circulated and printing is performed.

[0067] Furthermore, when both the pressurized tank liquid level sensor 32 and the negative pressure tank liquid level sensor 34 are turned off, the control unit 6 opens the ink supply valve 43. This allows ink to be supplied from the ink cartridge 41 to the negative pressure tank 33. When the negative pressure tank liquid level sensor 34 is turned on, the control unit 6 closes the ink supply valve 43.

[0068] When printing based on a print job is completed, the control unit 6 controls the pressure generation unit 23 of each ink unit 4 to terminate ink circulation in the ink circulation unit 21.

[0069] Next, the operation of the inkjet head 11 in the inkjet printing device 1 during maintenance will be explained with reference to the flowchart in Figure 6.

[0070] In step S1 of Figure 6, the control unit 6 controls each cap drive unit 13 to move each cap 12 to the capping position.

[0071] Next, in step S2, the control unit 6 controls the pressure generation unit 23 of each ink unit 4 to generate a purge pressure suitable for the lowest position nozzle 16 in the pressurized tank 31 of the ink circulation unit 21. This performs a pressurized purge in which ink is pushed out and discharged from each nozzle 16.

[0072] Next, in step S3, the control unit 6 determines whether a predetermined purge time has elapsed since the purge pressure was generated. If it determines that the purge time has not elapsed (step S3: NO), the control unit 6 repeats step S3.

[0073] If the control unit 6 determines that the purging time has elapsed (step S3: YES), in step S4, the control unit 6 controls the pressure generation unit 23 of each ink unit 4 to terminate the generation of purging pressure. This terminates the pressurized purging.

[0074] Next, in step S5, the control unit 6 controls each inkjet head 11 to perform flushing, except for the lowest nozzle 16. Specifically, the control unit 6 causes each inkjet head 11 to eject a preset amount of ink from each nozzle 16, except for the lowest nozzle 16, with the amount increasing as the nozzles are positioned higher.

[0075] Next, in step S6, the control unit 6 controls each cap drive unit 13 to move each cap 12 to the retracted position.

[0076] Next, in step S7, the control unit 6 controls the maintenance unit 5 to wipe the nozzle surface 11a of each inkjet head 11. Specifically, first, the control unit 6 positions the maintenance unit 5 in the deployed position. Then, the control unit 6 controls the wiper drive unit 52 to move the wiper unit 51 from a position above the upper inkjet head 11 to a position below the lower inkjet head 11.

[0077] As a result, each wiper 62 wipes the nozzle surface 11a of each inkjet head 11. This removes ink and other substances adhering to the nozzle surface 11a by pressurized purging. This completes the maintenance of the inkjet head 11. The ink and other substances removed from the nozzle surface 11a are collected in an ink receptacle (not shown).

[0078] Next, in step S8, the control unit 6 prints a test pattern to detect the nozzle 16 that is not ejecting ink. Specifically, the control unit 6 controls the printing unit 3 and each ink unit 4 to print a test pattern on the printing medium while the transport unit 2 transports the printing medium.

[0079] Next, in step S9, the control unit 6 determines, based on the print result of the test pattern, whether or not there is a non-ejecting nozzle 16 (a nozzle 16 that cannot eject ink) in at least one of the inkjet heads 11. Specifically, the control unit 6 acquires image data obtained by an image reading device (not shown) that reads the printed test pattern, analyzes the acquired image data, and determines whether or not there is a non-ejecting nozzle 16.

[0080] If it is determined that there is a nozzle 16 that is not dispensing ink (step S9: YES), in step S10, the control unit 6 performs the ink suction process described later. After this, the control unit 6 returns to step S7.

[0081] If the control unit 6 determines that there are no nozzles 16 that are not discharging (step S9: NO), the series of operations ends.

[0082] Next, the ink suction process performed in step S10 of Figure 6, as described above, will be explained with reference to the flowchart in Figure 7. The ink suction process is performed when there are nozzles 16 that are not ejecting ink after maintenance of the inkjet head 11.

[0083] In step S11 of Figure 7, the control unit 6 controls each cap drive unit 13 to move each cap 12 to the capping position.

[0084] Next, in step S12, the control unit 6 controls the pressure generation unit 23 of each ink unit 4 to generate a predetermined suction pressure, which is a negative pressure, in the waste ink tank 26. As a result, negative pressure is generated in the space inside each cap 12, and ink is drawn out from each nozzle 16 of each inkjet head 11. By drawing ink out from the nozzles 16, foreign matter such as thickened ink is removed from the nozzles 16, and non-discharge may be resolved.

[0085] Next, in step S13, the control unit 6 determines whether a predetermined suction time has elapsed since the suction pressure was generated. If it determines that the suction time has not elapsed (step S13: NO), the control unit 6 repeats step S13.

[0086] If the purge time has elapsed (step S13: YES), in step S14, the control unit 6 controls the pressure generating unit 23 of each ink unit 4 to terminate the generation of suction pressure. This terminates the suction of ink from each nozzle 16.

[0087] Next, in step S15, the control unit 6 controls each cap drive unit 13 to move each cap 12 to the retracted position. This completes the series of operations.

[0088] As explained above, in the inkjet printing apparatus 1, during maintenance of the inkjet head 11, the control unit 6 uses the pressure generation unit 23 to perform pressurized purging with a purging pressure suitable for the lowest position nozzle 16 in the inkjet head 11, thereby discharging ink from each nozzle 16. After pressurized purging, the control unit 6 controls each nozzle 16 other than the lowest position nozzle 16 to perform flushing with a larger ink discharge amount for higher position nozzles 16. This reduces waste ink by preventing an excessive amount of ink from being discharged from the inkjet head 11 due to pressurized purging.

[0089] Furthermore, if there are any non-ejecting nozzles 16 after maintenance of the inkjet head 11, the control unit 6 performs ink suction processing. This makes it possible to resolve any non-ejecting issues that were not resolved by maintenance.

[0090] In the embodiment described above, pressurized purging was performed at a purge pressure suitable for the lowest nozzle 16. However, this is not limited to this. Alternatively, a nozzle 16 other than the highest nozzle 16 could be used as a reference nozzle, and pressurized purging could be performed at a purge pressure suitable for the reference nozzle. Then, flushing could be performed on each nozzle 16 higher than the reference nozzle, with the amount of ink discharged increasing for nozzles at higher positions. This would reduce waste ink compared to the case where pressurized purging is performed at a purge pressure suitable for the highest nozzle 16.

[0091] Furthermore, the above-described embodiment described an inkjet printing apparatus 1 in which ink is ejected horizontally by an inkjet head 11 in which a plurality of nozzles 16 are arranged vertically. However, the present invention is not limited to this, and is applicable to inkjet printing apparatuses in which ink is ejected in a direction not perpendicular to the horizontal direction by an inkjet head in which a plurality of nozzles are arranged along a non-horizontal direction and the height position of each nozzle is different.

[0092] Furthermore, the above-described embodiment shows a configuration in which one ink supply unit 22 is provided for each ink circulation unit 21. However, the configuration is not limited to this, and a single ink supply unit may supply ink to multiple ink circulation units 21.

[0093] Furthermore, the above-described embodiment shows a configuration in which one ink unit 4 is provided for each inkjet head 11. However, the configuration is not limited to this, and a single ink unit may supply ink to multiple inkjet heads 11.

[0094] The present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiments.

[0095] [Note] This application discloses the following invention:

[0096] (Note 1) An inkjet head having multiple nozzles positioned at different heights, A purging unit that discharges ink from the multiple nozzles by pressurized purging, During maintenance of the inkjet head, the purge unit discharges ink from the multiple nozzles by pressurized purging at a purge pressure suitable for a reference nozzle, which is one of the multiple nozzles except the nozzle at the highest position. Then, the control unit controls the flushing of each nozzle that is positioned higher than the reference nozzle, so that the amount of ink discharged from the higher nozzle is greater. An inkjet printing apparatus characterized by comprising the following features.

[0097] (Note 2) The inkjet printing apparatus according to Appendix 1, characterized in that the reference nozzle is the nozzle at the lowest position among the plurality of nozzles.

[0098] (Note 3) The system further includes a suction unit that sucks ink from the aforementioned multiple nozzles, The inkjet printing apparatus according to Appendix 1 or 2, characterized in that, after maintenance of the inkjet head, if there is a nozzle that cannot eject ink, the suction unit controls the suction unit to suck ink from the plurality of nozzles. [Explanation of Symbols]

[0099] 1. Inkjet printing device 2. Conveying section 3 Printing Department 4 Ink Units 5. Maintenance Department 6 Control Unit 11 Inkjet heads 11a Nozzle surface 12 caps 13 Cap drive unit 14 Head holder 16 nozzles 21 Ink circulation unit 22 Ink Refill Section 23 Pressure generation unit 24 Pressurized air path 25. Negative pressure air path 26 Waste ink tank 27 Waste Ink Path 28. Suction air path 31 Pressurized tank 32 Pressurized tank liquid level sensor 33. Vacuum Tank 34. Vacuum Tank Liquid Level Sensor 35 Pressurized ink path 36. Negative pressure side ink path 37 Pump liquid delivery route 38 Ink pump 41 Ink Cartridges 42 Ink replenishment routes 43 Ink refill valve 51 Wiper Unit 52 Wiper drive unit 53 Guide rails 54 Connecting Members 61 Wiper base 62 wipers 66 Wiper motor 67 Ball screw

Claims

1. An inkjet head having multiple nozzles positioned at different heights, A purging unit that discharges ink from the multiple nozzles by pressurized purging, During maintenance of the inkjet head, the purge unit discharges ink from the multiple nozzles by pressurized purging at a purge pressure suitable for a reference nozzle, which is one of the multiple nozzles except the nozzle at the highest position. Then, the control unit controls the flushing of each nozzle that is positioned higher than the reference nozzle, so that the amount of ink discharged from the higher nozzle is greater. An inkjet printing apparatus characterized by comprising the following features.

2. The inkjet printing apparatus according to claim 1, characterized in that the reference nozzle is the nozzle at the lowest position among the plurality of nozzles.

3. The system further includes a suction unit that sucks ink from the aforementioned multiple nozzles, The inkjet printing apparatus according to claim 1 or 2, characterized in that the control unit controls the suction unit to suck ink from the plurality of nozzles if there are nozzles that cannot eject ink after maintenance of the inkjet head.

Images